Method to solve alignment mark blinded issues and technology for application of semiconductor etching at a tiny area

ABSTRACT

A method of unblinding an alignment mark comprising the following steps. A substrate having a cell area and an alignment mark within an alignment area is provided. An STI trench is formed into the substrate within the cell area. A silicon oxide layer is formed over the substrate, filling the STI trench and the alignment mark. The silicon oxide layer is planarized to form a planarized STI within the STI trench and leaving silicon oxide within the alignment mark to form a blinded alignment mark. A wet chemical etchant is applied within the alignment mark area over the blinded alignment mark to at least partially remove the silicon oxide within the alignment mark. The remaining silicon oxide is removed from within the blinded alignment mark to unblind the alignment mark. A drop etcher apparatus is also disclosed.

FIELD OF THE INVENTION

[0001] The present invention relates generally to semiconductorfabrication and more specifically to alignment marks and semiconductoretching at tiny areas.

BACKGROUND OF THE INVENTION

[0002] Alignment marks are used to permit precise alignment ofphotolithographic masks with the wafer during masking steps to minimizemisalignment between multiple layers. However, the alignment marks are‘blinded’ after non-ODR shallow trench isolation (STI) chemicalmechanical polishing (CMP) processes. This prevents transfer of thelower alignment mark to the next, upper layer, for example a metallayer.

[0003] An additional photolithography and etching step (ODR) arerequired to clear out the silicon oxide residue from the ‘blinded’alignment mark field. This increases costs, increases the cycle time andmanufacture loading. Further, the ODR approach is limited by the circuitdesign rule especially as the design rule passes 0.1 μm logic andbeyond.

[0004] Blind alignment marks will become a critical issue in non-ODreverse tone photo/etch (ODR) processes after 0.1 μm and beyond shallowtrench isolation (STI) CMP.

[0005] U.S. Pat. No. 6,194,287 B1 to Jang et al. describes an STIprocess and reverse mask to clear off alignment marks.

[0006] U.S. Pat. No. 6,080,635 to Jang et al. describes discloses amethod to preserve alignment marks with STI processes.

[0007] U.S. Pat. No. 6,043,133 to Jang et al. describes a process toimprove STI removal over alignment marks.

[0008] U.S. Pat. No. 6,015,744 to Tseng describes a clear out andalignment mark process.

[0009] U.S. Pat. No. 5,188,258 to Iwashita describes a quantitativefluid discharge device.

SUMMARY OF THE INVENTION

[0010] Accordingly, it is an object of one or more embodiments of thepresent invention to provide an improved method of unblinding alignmentmarks.

[0011] Other objects will appear hereinafter.

[0012] It has now been discovered that the above and other objects ofthe present invention may be accomplished in the following manner.Specifically, a substrate having a cell area and an alignment mark areais provided. The substrate having an alignment mark within the alignmentmark area. An STI trench is formed into the substrate within the cellarea. A silicon oxide layer is formed over the substrate, filling theSTI trench and the alignment mark. The silicon oxide layer is planarizedto form a planarized STI within the STI trench and leaving silicon oxidewithin the alignment mark to form a blinded alignment mark. A wetchemical etchant is applied within the alignment mark area over theblinded alignment mark to at least partially remove the silicon oxidewithin the alignment mark. The remaining silicon oxide is removed fromwithin the blinded alignment mark to unblind the alignment mark. A dropetcher apparatus is also disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention will be more clearly understood from thefollowing description taken in conjunction with the accompanyingdrawings in which like reference numerals designate similar orcorresponding elements, regions and portions and in which:

[0014] FIGS. 1 to 6 schematically illustrate a preferred embodiment ofthe present invention.

[0015]FIG. 7 schematically illustrates a drop etcher used with thepreferred embodiment of the present invention.

[0016]FIG. 8 is an enlarged cross-section of FIG. 7 taken at the dashedcircle labeled “FIG. 8.”

[0017]FIG. 9 is an enlarged cross-section of FIG. 7 taken at the dashedcircle labeled “FIG. 9.”

[0018]FIGS. 10a, 10 b and 10 c are respective graphs of: voltage vs.time on of the signal from the controller; pressure vs. time; and thechemical drop vs. time.

[0019]FIG. 11A is an enlarged schematic representation of a portion thedrop etcher illustrated in FIG. 7 used with a blanket wafer monitor.

[0020]FIG. 11B is a graph of an etching profile of a blanket wafermonitor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0021] The inventors have discovered a novel method to solve thealignment mark (AM) blinding issues that includes using a wet chemicalsolution to partially remove the oxide residue within the blindedalignment marks after STI CMP processing. Furthermore, the wet chemicalsolution oxide residue removal easily integrates into the subsequentsilicon nitride (Si₃N₄ or SiN) strip step.

[0022] Initial Structure

[0023] As shown in FIG. 1, structure 10 is preferably a siliconsubstrate and includes an overlying layer 12 lining alignment marks 16within alignment mark area 20. Layer 12 is preferably comprised ofsilicon nitride (Si₃N₄ or SiN) or polysilicon (having a thickness offrom about 500 to 2000 Å) and is more preferably SiN as will be used forillustrative purposes hereafter. SiN layer 12 is preferably from about100 to 2000 Å and more preferably from about 800 to 1100 Å thick.

[0024] Alignment marks 16 have a depth of preferably from about 1150 to1250 Å and more preferably about 1200 Å. Alignment marks 16 have a widthof preferably from about 7.8 to 8.2 μm and more preferably about 8.0 μm.

[0025] A shallow trench isolation (STI) opening 14 is formed through theSiN layer 12 and into silicon substrate 10 within cell area 18 that isspaced apart form alignment mark area 20.

[0026] Formation of Oxide Layer 22

[0027] To form the STI, a silicon oxide (oxide) layer 22 is formed oversilicon substrate 10, filling STI trench 14 and alignment marks 16.Alignment marks 16 are filled by oxide layer 22 and by the oxide residueformed by the CMP of oxide layer 22 to form planarized STI layer 22′(see below).

[0028] Planarization of Oxide Layer 22

[0029] Oxide layer 22 is then planarized, preferably by a chemicalmechanical polishing (CMP) process to form planarized STI 22′ andfilling (and ‘blinding’) alignment marks 16 with oxide 22″.

[0030] Use of Drop Etcher 40

[0031] As shown in FIG. 4, a drop etcher 40 (such as that shown in FIG.7) is aligned and used to dispense a wet etching chemical 25 in the formof a drop 26 only over the oxide filled 22″ alignment marks 16 withinalignment mark area 20. The planarized STI 22′ is not contacted with, oraffected by, wet etching chemical 25. The tip 24 of drop etcher 40 isaligned with the ‘blinded’ alignment marks 16 by finding water notch orby pattern recognition (align cell pattern).

[0032] Wet etching chemical 25 is preferably hydrogen fluoride (HF) orbuffered oxide etchant (BOE). If BOE is used, it has an oxide:SiNetching sensitivity of about 10:1 with an oxide etching rate of about1400 Å/min. If HF is used, it has an oxide:SiN etching sensitivity ofabout 15:1 with an oxide etching rate of about 9000 Å/min.

[0033] As shown in FIGS. 7 to 9, drop etcher 40 may include a controlunit 30 that dispenses a measured amount of wet etching chemical 25,preferably in the form of a drop 26, from within dispenser tube 34(having inside diameter 52) through tip 24 to wafer 10 by using pressure50.

[0034] Line 51 connects control unit 30 to the upper portion ofdispenser tube 34 and through which line 51 a gas, such as preferablyair or nitrogen (N₂), is pulsed through a filter 60, a pressureregulator 62 and a high-speed shut-off valve 64 controlled 66 by thecontroller 30 or a timer.

[0035]FIGS. 10a, 10 b and 10 c respectively illustrate: voltage vs. theamount of time on t_(on) of the signal 66 from the controller 30 or atimer; pressure vs. time; and the chemical drop 26 vs. time wherein:

chemical drop 26=(t _(on) *Xr**Xp***)

[0036]

[0037] with the shut-off valve 64 radius (r) being preferably from about0.05 to 5.00 mm and is more preferably from about 0.01 to 8.00 mm.

[0038] The time control is preferably from about 0.001 to 10.000 secondsand more preferably from about 0.001 to 5.000 seconds; the pressurecontrol is preferably from about 0.001 to 10.000 psi and more preferablyfrom about 0.001 to 5.000 psi; the tip 24 inside diameter 54 ispreferably from about 0.01 to 2.00 mm and more preferably from about0.10 to 1.00 mm; and the dispenser distance 70 is preferably from about1.0 μm to 1.0 cm and more preferably from about 0.5 to 6.0 mm.

[0039] As illustrated in FIGS. 8 and 9 (and see FIG. 4), upon theapplication of gas pressure 50 onto the upper surface 72 of the chemical25 within the dispenser tube 34, the pressure 50 of the gas expels aportion of the chemical 25 through the drop etcher tip 24 to form a drop26 as the level of the chemical 25 within the dispenser tube 34 islowered to the dashed upper surface line 74.

[0040] By the precise control of the gas pressure, time and size of thetips and nozzles involved, consistent deposits are ensured with asped-up output while maintaining high quality and reduced waste. Byincreasing either the gas pressure, the time duration or the tip gauge(inside diameter 54), the size of the drop and hence the etch size willincrease.

[0041] The tip 24 is preferably comprised of a non-reactive materialsuch as polytetrafluorethylene (PTFE), perfluoroalkoxy (PFA), orpolyvinyl chloride (PVC). For wet dip process optimization, the tip 24preferably has: an outer diameter 56 of preferably from about 0.5 to 3.0mm and more preferably about 1.0 mm; and an inner diameter 54 ofpreferably from about 0.5 to 0.7 mm and more preferably about 0.5 mm.

[0042] The tip 24 is preferably spaced from the upper surface of thestructure 10 a dispenser distance 70 of preferably from about 1 μm to 1cm and more preferably from about 0.5 mm to 6.0 mm.

[0043] In real process control, the drop 26 has an inner diameter 100 offrom about 0.1 to 0.7 mm and an outer diameter of from about 1.0 to 3.0mm (see FIG. 4). This ensures that the wet etching chemical drop 26covers the oxide 22″ filled alignment marks 16 within alignment markarea 20 without impinging upon the cell area 18 and the STI 22′.

[0044] Etching of Oxide 22″ Within Alignment Marks 16

[0045] As shown in FIG. 5, the etching chemical drop 26 etches the oxide22″ within alignment marks 16 so that preferably from about 80 to 90% ofthe oxide 22″ within alignment marks 16 is removed and more preferablyfrom about 85 to 90% in from about 10 to 100 seconds and more preferablyfrom about 30 to 45 seconds.

[0046] The remainder of drop 26 is removed before the SiN strip step(see below).

[0047] SiN Layer 12 Strip

[0048] As shown in FIG. 6, SiN layer 12 is then stripped and removedfrom silicon substrate 10 and from within alignment marks 16 using a SiNstripping process that is preferably a wet bench clean process. Thisalso removes any remaining oxide 22″ from alignment marks 16 and any wetetching chemical 25/oxide 22 residue from silicon substrate 10. The SiNstripping process preferably uses H₃PO₄.

[0049] Thus, alignment marks 16 are now clear and transparent to thenext formed layer, such as a metal layer, so that the alignments marks16 are transferred to the upper, next formed layer and may be readilyobserved for continued fabrication.

[0050]FIG. 11A is an enlarged schematic representation of a portion thedrop etcher 24″ illustrated in FIG. 7 illustrating the inside diameter(ID) and outside diameter (OD) of an etched opening 102 shown in dashedline after a drop 100 from drop etcher 24″ is released from drop etcher24″ onto a monitor wafer's oxide layer 12″ over silicon substrate 10″.The ID and OD are plotted in FIG. 11B (see below).

[0051]FIG. 11B is a graph of blanket wafer monitor etch rate and etchprofile (not in real application) where CPVC is chlorinated polyvinylchloride and the mean of BOE of 2:1 is a mixed ratio of about 40% NH₄Fto about 49% HF 2:1.

[0052] Advantages of the Present Invention

[0053] The advantages of one or more embodiments of the presentinvention include:

[0054] 1. saves the time and expense of an additional ODR;

[0055] 2. the method is simple and inexpensive;

[0056] 3. the method is easy to integrate with the SiN strippingprocess;

[0057] 4. current dispenser technology is available for the droptechnology used in the present invention; and

[0058] 5. increase STI CMP process merge.

[0059] While particular embodiments of the present invention have beenillustrated and described, it is not intended to limit the invention,except as defined by the following claims.

We claim:
 1. A method of unblinding an alignment mark, comprising thesteps of: providing a substrate having a cell area and an alignment markarea; the substrate having an alignment mark within the alignment markarea; forming an STI trench into the substrate within the cell area;forming a silicon oxide layer over the substrate, filling the STI trenchand the alignment mark; planarizing the silicon oxide layer to form aplanarized STI within the STI trench and leaving silicon oxide withinthe alignment mark to form a blinded alignment mark; applying a wetchemical etchant within the alignment mark area over the blindedalignment mark to at least partially remove the silicon oxide within thealignment mark; and removing the remaining silicon oxide from within theblinded alignment mark to unblind the alignment mark.
 2. The method ofclaim 1, including the step of forming a layer over the substrate andlining the alignment mark before the formation of the STI trench intothe substrate.
 3. The method of claim 1, wherein the structure is asemiconductor substrate.
 4. The method of claim 1, wherein the structureis comprised of silicon.
 5. The method of claim 1, including the step offorming a layer over the substrate and lining the alignment mark beforethe formation of the STI trench into the substrate; wherein thestructure is comprised of silicon and the layer is comprised of amaterial selected from the group consisting of: SiN and polysilicon. 6.The method of claim 1, including the step of forming a layer over thesubstrate and lining the alignment mark before the formation of the STItrench into the substrate; wherein the structure is comprised of siliconand the layer is comprised of a material selected from the groupconsisting of: SiN.
 7. The method of claim 1, including the step offorming a layer over the substrate and lining the alignment mark beforethe formation of the STI trench into the substrate; wherein the layer iscomprised of SiN and is from about 100 to 2000 Å thick and the alignmentmark has a depth of from about 1150 to 1250 Å and a width of from about7.8 to 8.2 μm.
 8. The method of claim 1, including the step of forming alayer over the substrate and lining the alignment mark before theformation of the STI trench into the substrate; wherein the layer iscomprised of SiN and is from about 800 to 1100 Å thick and the alignmentmark has a depth of about 1200 Å and a width of about 8.0 μm.
 9. Themethod of claim 1, wherein the silicon oxide layer is planarized bychemical mechanical polishing.
 10. The method of claim 1, wherein thewet chemical etchant is comprised of a chemical selected from the groupconsisting of HF and BOE.
 11. The method of claim 1, wherein the wetchemical etchant is applied to the blinded alignment mark in the form ofa drop.
 12. The method of claim 1, wherein the wet chemical etchant isapplied to the blinded alignment mark from a drop etcher.
 13. The methodof claim 1, wherein the wet chemical etchant is applied to the blindedalignment mark from a drop etcher having a tip with an inner diameter offrom about 0.5 to 0.7 mm.
 14. The method of claim 1, wherein from about80 to 90% of the silicon oxide is removed from the blinded alignmentmark by the wet chemical etchant.
 15. The method of claim 1, whereinfrom about 85 to 90% of the silicon oxide is removed from the blindedalignment mark by the wet chemical etchant.
 16. The method of claim 1,including the step of forming a layer over the substrate and lining thealignment mark before the formation of the STI trench into thesubstrate; wherein the layer is comprised of SiN and is removed by a wetbench clean process.
 17. The method of claim 1, wherein the wet chemicaletchant is applied to the blinded alignment mark in the form of a dropfrom a drop etcher dispenser tube; the drop being dispensed from thedispenser tube through the application of gas pressure.
 18. The methodof claim 1, wherein the wet chemical etchant is applied to the blindedalignment mark in the form of a drop from a drop etcher dispenser tube;the drop being dispensed from the dispenser tube through the applicationof gas pressure; the gas pressure being applied through a high speedshut-off valve from a gas source.
 19. The method of claim 1, wherein thewet chemical etchant is applied to the blinded alignment mark in theform of a drop from a drop etcher dispenser tube; the drop beingdispensed from the dispenser tube through the timed application of gaspressure; the gas pressure being applied through a high speed shut-offvalve from a gas source; the shut-off valve having a radius; the amountof the drop equal to the length of the timed application of the gaspressure multiplied by the radius of the shut-off valve multiplied bythe amount of the gas pressure.
 20. The method of claim 1, wherein thewet chemical etchant is applied to the blinded alignment mark in theform of a drop from a drop etcher dispenser tube; the drop beingdispensed from the dispenser tube through the timed application of gaspressure; the gas pressure being applied through a high speed shut-offvalve from a gas source; the shut-off valve having a radius; the amountof the drop equal to the length of the timed application of the gaspressure multiplied by the radius of the shut-off valve multiplied bythe amount of the gas pressure; the length of the timed application ofthe gas pressure being from about 0.001 to 5.000 seconds; the radius ofthe shut-off valve being from about 0.05 to 5.00 mm; and the amount ofthe gas pressure being from about 0.001 to 5.000 psi.
 21. The method ofclaim 1, wherein the wet chemical etchant is applied to the blindedalignment mark in the form of a drop from a drop etcher dispenser tube;the drop being dispensed from the dispenser tube through the timedapplication of gas pressure; the gas pressure being applied through ahigh speed shut-off valve from a gas source; the shut-off valve having aradius; the amount of the drop equal to the length of the timedapplication of the gas pressure multiplied by the radius of the shut-offvalve multiplied by the amount of the gas pressure; the length of thetimed application of the gas pressure being from about 0.001 to 10.000seconds; the radius of the shut-off valve being from about 0.05 to 5.00mm; and the amount of the gas pressure being from about 0.01 to 10.00psi.
 22. The method of claim 1, wherein the wet chemical etchant isapplied to the blinded alignment mark in the form of a drop from a dropetcher dispenser tube; the drop being dispensed from the dispenser tubethrough the application of gas pressure through a pressure regulator anda high-speed valve.
 23. A method of unblinding an alignment mark,comprising the steps of: providing a substrate having a cell area and analignment mark area; the substrate having an alignment mark within thealignment mark area; forming an SiN layer over the substrate and liningthe alignment mark; forming an STI trench through the SiN layer and intothe substrate within the cell area; forming a silicon oxide layer overthe substrate, filling the STI trench and the SiN layer lined alignmentmark; planarizing the silicon oxide layer to form a planarized STIwithin the STI trench and leaving silicon oxide within the alignmentmark to form a blinded alignment mark; applying a wet chemical etchantwithin the alignment mark area over the blinded alignment mark to atleast partially remove the silicon oxide within the alignment mark; andremoving the SiN layer from over the substrate and within SiN layerlined alignment mark whereby the silicon oxide is also removed fromwithin the blinded alignment mark to unblind the alignment mark.
 24. Themethod of claim 23, wherein the substrate is a semiconductor substrate.25. The method of claim 23, wherein the substrate is comprised ofsilicon.
 26. The method of claim 23, wherein the alignment mark has adepth of from about 1150 to 1250 Å and a width of from about 7.8 to 8.2μm.
 27. The method of claim 23, wherein the SiN layer is from about 100to 2000 Å thick.
 28. The method of claim 23, wherein the silicon oxidelayer is planarized by chemical mechanical polishing.
 29. The method ofclaim 23, wherein the wet chemical etchant is comprised of a chemicalselected from the group consisting of HF and BOE.
 30. The method ofclaim 23, wherein the silicon oxide layer is planarized by chemicalmechanical polishing and the wet chemical etchant is comprised of achemical selected from the group consisting of HF and BOE.
 31. Themethod of claim 23, wherein the wet chemical etchant is applied to theblinded alignment mark in the form of a drop.
 32. The method of claim23, wherein the wet chemical etchant is applied to the blinded alignmentmark from a drop etcher.
 33. The method of claim 23, wherein the wetchemical etchant is applied to the blinded alignment mark from a dropetcher having a tip with an inner diameter of from about 0.5 to 0.7 mm.34. The method of claim 23, wherein from about 80 to 90% of the siliconoxide is removed from the blinded alignment mark by the wet chemicaletchant.
 35. The method of claim 23, wherein from about 85 to 90% of thesilicon oxide is removed from the blinded alignment mark by the wetchemical etchant in from about 10 to 100 seconds.
 36. The method ofclaim 23, wherein the SiN layer and is removed by a wet bench cleanprocess.
 37. The method of claim 23, wherein the wet chemical etchant isapplied to the blinded alignment mark in the form of a drop from a dropetcher dispenser tube; the drop being dispensed from the dispenser tubethrough the application of gas pressure.
 38. The method of claim 23,wherein the wet chemical etchant is applied to the blinded alignmentmark in the form of a drop from a drop etcher dispenser tube; the dropbeing dispensed from the dispenser tube through the application of gaspressure; the gas pressure being applied through a high speed shut-offvalve from a gas source.
 39. The method of claim 23, wherein the wetchemical etchant is applied to the blinded alignment mark in the form ofa drop from a drop etcher dispenser tube; the drop being dispensed fromthe dispenser tube through the timed application of gas pressure; thegas pressure being applied through a high speed shut-off valve from agas source; the shut-off valve having a radius; the amount of the dropequal to the length of the timed application of the gas pressuremultiplied by the radius of the shut-off valve multiplied by the amountof the gas pressure.
 40. The method of claim 23, wherein the wetchemical etchant is applied to the blinded alignment mark in the form ofa drop from a drop etcher dispenser tube; the drop being dispensed fromthe dispenser tube through the timed application of gas pressure; thegas pressure being applied through a high speed shut-off valve from agas source; the shut-off valve having a radius; the amount of the dropequal to the length of the timed application of the gas pressuremultiplied by the radius of the shut-off valve multiplied by the amountof the gas pressure; the length of the timed application of the gaspressure being from about 0.001 to 5.000 seconds; the radius of theshut-off valve being from about 0.05 to 5.00 mm; and the amount of thegas pressure being from about 0.001 to 5.000 psi.
 41. The method ofclaim 23, wherein the wet chemical etchant is applied to the blindedalignment mark in the form of a drop from a drop etcher dispenser tube;the drop being dispensed from the dispenser tube through the timedapplication of gas pressure; the gas pressure being applied through ahigh speed shut-off valve from a gas source; the shut-off valve having aradius; the amount of the drop equal to the length of the timedapplication of the gas pressure multiplied by the radius of the shut-offvalve multiplied by the amount of the gas pressure; the length of thetimed application of the gas pressure being from about 0.001 to 10.000seconds; the radius of the shut-off valve being from about 0.05 to 5.00mm; and the amount of the gas pressure being from about 0.001 to 10.000psi.
 42. The method of claim 23, wherein the wet chemical etchant isapplied to the blinded alignment mark in the form of a drop from a dropetcher dispenser tube; the drop being dispensed from the dispenser tubethrough the application of gas pressure through a pressure regulator anda high-speed valve.
 43. A drop etcher apparatus, comprising: a controlunit; a dispenser tube having: an upper end; and a lower tip proximatean upper surface of a structure; a chemical reservoir at least partiallyfilling the dispenser tube; the chemical reservoir having an initialupper surface; and a dispenser line connecting the control unit to theupper end of the dispenser tube through which a gas under pressure flowsas controlled by the control unit to dispense a drop of the chemicalthrough the lower tip to the surface of the structure by exertion ofpressure from the gas flowing through the dispenser line to the initialupper surface of the chemical reservoir.
 44. The apparatus of claim 43,further including a filter interposed in the dispenser line throughwhich the gas flows to filter the gas.
 45. The apparatus of claim 43,further including a pressure regulator interposed in the dispenser linethrough which the gas flows to regulate the pressure of the gas.
 46. Theapparatus of claim 43, further including a high-speed shut-off valveinterposed in the dispenser line through which the gas flows to regulatethe flow of the gas.
 47. The apparatus of claim 43, further including afilter interposed in the dispenser line through which the gas flows tofilter the gas; a pressure regulator interposed in the dispenser linethrough which the gas flows to regulate the pressure of the gas; and ahigh-speed shut-off valve interposed in the dispenser line through whichthe gas flows to regulate the flow of the gas.
 48. The apparatus ofclaim 43, further including: a high-speed shut-off valve interposed inthe dispenser line through which the gas flows to regulate the flow ofthe gas; the shut-off valve having a radius; wherein the amount of thedrop equal to: the length of the timed application of the gas pressuremultiplied by the radius of the shut-off valve multiplied by the amountof the gas pressure.
 49. The apparatus of claim 43, wherein the lowertip has an inside diameter of from about 0.1 to 1.0 mm.
 50. Theapparatus of claim 43, wherein the lower tip has an inside diameter offrom about 0.01 to 2.00 mm.
 51. The apparatus of claim 43, wherein thegas introduced into the dispenser tube has a pressure of from about0.001 to 5.000 psi.
 52. The apparatus of claim 43, wherein the gasintroduced into the dispenser tube has a pressure of from about 0.001 to10.000 psi.
 53. The apparatus of claim 43, wherein the gas introducedinto the dispenser tube has a pressure of from about 0.001 to 5.000 psiand flows through the dispenser line for from about 0.001 to 5.000seconds.
 54. The apparatus of claim 43, wherein the gas introduced intothe dispenser tube has a pressure of from about 0.001 to 5.000 psi andflows through the dispenser line for from about 0.001 to 10.000 seconds.